Are the safest MPs the most dodgy?

A reference from Polly Toynbee has turned a LibDem blogger into the expert on links between MPs' super majorities and their expenses claims. Here he explains what he found
• All the latest MPs' claims listed

The ceremonial Mace of the house of commons. Photograph: Peter Macdiarmid/Getty Images

Mark Thompson

Friday 29 May 2009 04.34 EDT
First published on Friday 29 May 2009 04.34 EDT

Two weeks ago I was walking my dog when I started wondering, could our electoral system have contributed to the scandal of MPs' expenses? I thought it might be a good subject for a post on my political blog Mark Reckons.

My reasoning was that in our First Past the Post system, there are a lot of safe seats. In a typical General Election maybe a hundred or so change hands between the parties. In a landslide this can go up but you still have maybe two thirds of MPs who have very little to worry about.I then wondered if there was any sort of correlation between how safe a seat is and the likelihood of its MP being involved in the expenses scandal. I decided to go through the data to see.

Firstly, I found a list of all MPs from 2005 on this Keele university website. I took this data and put it into MS Excel and then sorted the MPs so that they are ordered by majority, largest to smallest and numbered 1 for the largest, 2 for the second largest and so on.

Then I totalled up all the numbers and divided this by the number of MPs involved (94 at that point). The results I published on Sunday 17th May were quite striking:

MP expenses analysis Photograph: Public Domain

As you can see there is a clear gradation in each quartile indicating a correlation between the safety of the seat, and the likelihood of the MP being implicated.

The response was amazing — my most-viewed post ever with thousands of people visiting it, linked to by Polly Toynbee as well as Iain Dale, Guido Fawkes - and many other political bloggers. It also led to me being interviewed for Radio 4's More or Less.

I updated the data this Wednesday with the latest list of 243 implicated MPs. The results are:

MP expenses graph 2 Photograph: Public Domain

There is still an increase in each quartile. It is less pronounced than previously - but there is still a stark difference between the bottom and the top, with the top having almost twice as many as the bottom.

One of the objections to this analysis is that the Telegraph are bound to focus on the most high profile MPs first. But almost three weeks in that effect must surely have dissipated as they ran out of high profile ones. I certainly found myself doing this update wondering who a lot of the newly added MPs are. I hadn't heard of lots of them and I'm a political anorak.

As you can see if you follow the links to my blog above, there are lots of comments and it has sparked a debate. Some feel there are problems with the approach and methodology, others think it is OK. I had a fellow Lib Dem blogger Andy Hinton run some statistical tests on the original data which I think helps confirm their robustness - to an extent.

It is a good start but more work is needed once all the data is in the public domain. I hope others with a more statistical background can come up with a more definitive way of measuring any effect there might be there.Of course, a system that eliminated safe seats would mean any link that may eventually be proven would also be eliminated.

•Mark Thompson is a Lib Dem activist, political obsessive, company director and computer programmer. He is not the Director General of the BBC. You can follow him on Twitter @MarkReckons